Glennon was named the starter following the dismissal of Marcus Vick and held that job until being replaced by Tyrod Taylor during the 2007 season.

Glennon's younger brother, Mike, played collegiately as a quarterback at NC State and for several teams in the NFL.

John, his father, had a position with ExxonMobil that forced the family to move three times in Sean's grade-school years.

From The Woodlands, the family would move to New Jersey, back to Texas, then finally to Centreville, Virginia, where they would stay for Glennon's high school years.

Over the next year, his final (senior) season at Westfield High School, Glennon led the Bulldogs to a 14–0 record and the 2003 Virginia AAA Division 6 state championship, beating Landstown 35–14 .

Following the championship season, Glennon received numerous accolades as he finalized his search for a college choice.

[2] Due to his numerically successful high school career and the number of awards granted him, Glennon was widely recruited by college teams eager to find a stable quarterback.

After visiting the campuses of each school, Glennon made his decision, committing to Virginia Tech on August 14, 2003.

As Marcus Vick returned from his suspension from the Virginia Tech football team to assume the starting quarterback role, Sean Glennon asked for and was granted a redshirt season in 2005.

[3] In the Hokies' season-opening win over Northeastern University, Glennon completed 15 of his 18 passes for a total of 222 yards, three touchdowns, and one interception.

Glennon started the first two games of the Hokies' 2008 season: a loss to the East Carolina Pirates and a victory over the Furman Paladins.

[11] Glennon came in a few weeks later against Florida State, where he threw for 122 yards and a touchdown before leaving the game with a sprained ankle.

On a Thursday night two weeks later against Maryland, Glennon lead his team to victory with a 14–20, 127 yard 1 TD performance against the Terps.